1. Field of the Invention
The present invention relates to a pallet changer for changing pallets between a machine table in a machining center and a pallet changing position in a pallet pool.
2. Description of the Related Art
In a certain type of pallet changer for changing pallets between a machine table in a machining center and a pallet changing position in a pallet pool, a rotary table capable of supporting two pallets at a time is disposed between the machine table and the pallet changing position. A pallet to be carried onto the machine table is carried onto one end of the rotary table in advance from the pallet changing position and is allowed to stand by there. Upon completion of machining, the pallet on the machine table is carried onto the other end of the rotary table. Thereafter, the rotary table is turned 180.degree. whereby the pallet to be machined is transferred onto the machine table from the rotary table. In another type of a pallet changer, a pallet pool is disposed in proximity to a machine table. Upon completion of machining, the pallet on the machine table is carried to a vacant pallet changing position in the pallet pool, thereafter the pallet to be carried onto the machine table is indexed to the pallet changing position and then transferred onto the machine table.
In the former type, the provision of the rotary table requires a fairly increased floor space and the shortening of the pallet changing time encounters a limit because of a large number of operations required for pallet changing (carrying out.fwdarw.turning.fwdarw.carrying in).
In the latter type, too, it is impossible to expect shortening of the pallet changing time, although the drawback on the floor space can be overcome. Particularly, the latter type requires a pallet pool indexing operation during pallet changing and therefore a great increase of the pallet changing time is unavoidable.